Submission #784219

#	Time	Username	Problem	Language	Result	Execution time	Memory
784219		Ozy	Highway Tolls (IOI18_highway)	C++17	0 / 100	208 ms	262144 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
#define lli long long int
#define debug(a) cout << #a << " = " << a << endl
#define debugsl(a) cout << #a << " = " << a << ", "
#define rep(i,a,b) for(int i = (a); i <= (b); i++)
#define repa(i,a,b) for(int i = (a); i >= (b); i--)
#define pll pair<lli,lli>

#define MAX 90000
//para los hijos
#define des first
#define id second

lli m,df,prof,sz;
lli arista_padre[MAX+2],tam[MAX+2],color[MAX+2];
vector<pll> hijos[MAX+2];
vector<lli> nodos,inval;
vector<int> status;

void pre_process(lli pos, lli padre) {
    tam[pos] = 1;
    color[pos] = 2;
    for(auto h : hijos[pos]) {
        if(padre == h.des || inval[h.id] == 1) continue;
        pre_process(h.des,pos);
        tam[pos] += tam[h.des];
    }
}

lli busca(lli pos, lli padre, lli lim) {

    for(auto h : hijos[pos]) {
        if (padre == h.des || inval[h.id] == 1) continue;
        if (tam[h.des] >= lim) return busca(h.des,pos,lim);
    }
    return pos;
}

void marca(lli pos, lli padre, lli ari, lli c) {
    status[ari] = c;
    color[ari] = c;
    for(auto h : hijos[pos]) {
        if (h.des == padre || inval[h.id] == 1) continue;
        marca(h.des,pos,h.id,c);
    }
}

void dfs(lli pos, lli padre, lli p,lli c) {

    if(p == prof) {
        nodos.push_back(pos);
        return;
    }

    for(auto h : hijos[pos]) {
        if(padre == h.des || color[h.id] != c || inval[h.id] == 1) continue;
        arista_padre[h.des] = h.id;
        dfs(h.des,pos,p+1,c);
    }
}

lli solve(lli raiz,lli prof,lli c) {

    if(prof == 0) return raiz;
    nodos.clear();

    dfs(raiz,-1,0,c);

    lli last,ini = 0;
    lli mitad,fin = nodos.size()-1;
    while (ini <= fin) {
        mitad = (ini+fin)/2;
        rep(i,0,nodos.size()-1) {
            if (ini <= i && i <= mitad) status[ arista_padre[nodos[i]] ] = 1;
            else status[arista_padre[nodos[i]]] = 0;
        }

        lli x = ask(status);
        if (x != df) {
            fin = mitad-1;
            last = mitad;
        }
        else ini = mitad+1;
    }

    return(nodos[last]);

}

void find_pair(int n, std::vector<int> u, std::vector<int> v, int A, int B) {

    m = u.size();
    rep(i,0,m-1) {
        hijos[u[i]].push_back({v[i],i});
        hijos[v[i]].push_back({u[i],i});
    }

    status.resize(m);
    inval.resize(m,0);

    rep(i,0,m-1) status[i] = 0;
    df = ask(status);
    sz = df/A;

    //busca centroid
    lli raiz = 0;
    lli p0,p1;
    do {
        pre_process(raiz,-1); // tambien limpia los colores

        if(tam[raiz] == 2) {
            for(auto h : hijos[raiz]) {
                if (inval[h.id] == 0) answer(raiz,h.des);
                return;
            }
        }

        lli mitad = tam[raiz]/2;
        lli act = busca(raiz,-1,mitad);
        //dividelo en los 2 colores
        lli unos = 0;

        rep(i,0,m-1) status[i] = 0;
        for(auto h : hijos[act]) {
            if (inval[h.des] == 1) continue;
            if (tam[h.des]+unos <= mitad) {
                marca(h.des,act,h.id,1);
                unos += tam[h.des];
            }
            else marca(h.des,act,h.id,0);
        }
        //corregido

        lli x = ask(status);
        lli big = (x - df)/(B-A);

        raiz = act;
        if (big == sz) rep(i,0,m-1) if(color[i] == 0) inval[i] = 1;
        else if (big == 0) rep(i,0,m-1) if(color[i] == 1) inval[i] = 1;
        else {
            p1 = big;
            p0 = sz-big;
            break;
        }

    } while(true);

    //pregunta por ambas raices y reporta el resultado
    lli x = solve(raiz,p0,0);
    lli y = solve(raiz,p1,1);

    answer(x,y);

}

Compilation message (stderr)

highway.cpp: In function 'long long int solve(long long int, long long int, long long int)':
highway.cpp:7:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 | #define rep(i,a,b) for(int i = (a); i <= (b); i++)
      |                                       ^
highway.cpp:75:9: note: in expansion of macro 'rep'
   75 |         rep(i,0,nodos.size()-1) {
      |         ^~~
highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:141:17: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  141 |         else if (big == 0) rep(i,0,m-1) if(color[i] == 1) inval[i] = 1;
      |                 ^
highway.cpp:140:12: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
  140 |         if (big == sz) rep(i,0,m-1) if(color[i] == 0) inval[i] = 1;
      |            ^
highway.cpp: In function 'long long int solve(long long int, long long int, long long int)':
highway.cpp:88:22: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized]
   88 |     return(nodos[last]);
      |                      ^

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 0 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31